Electric retractable view device for vehicle, and shaft outside-fitting gear incorporated in the device

ABSTRACT

Solving a problem in strength that occurs as a result of forming a shaft outside-fitting gear for an electric retractable view device for a vehicle, using a material including a resin as a base material. A shaft outside-fitting gear is formed of a material including a resin as a base material. The gear includes a clutch surface in one end face in an axis direction thereof. The clutch surface is disposed on an inner circumferential side and an outer circumferential side of a radial position of a tooth bottom of each gear tooth of the gear relative to the radial position of the tooth bottom, in a radial direction of the gear. One end face in the axis direction of the gear has a structure in which a valley of each gear tooth of the gear is occluded at a radial region at which the clutch surface is disposed.

TECHNICAL FIELD

This invention relates to an electric retractable view device for a vehicle such as an electric retractable mirror for a vehicle or an electric retractable camera for a vehicle, the electric retractable view device solving a problem in strength that occurs as a result of forming a gear fitted on an outer circumference of a shaft so as to be rotatable in a direction around an axis of the shaft (in the present application, this gear is referred to as “shaft outside-fitting gear”), using a material including a resin as a base material. Also, this invention relates to a shaft outside-fitting gear to be incorporated in an electric retractable view device for a vehicle.

BACKGROUND ART

Shaft outside-fitting gears in conventional electric retractable mirrors for a vehicle are generally made of metal. Examples of the conventional electric retractable mirrors include those described in Patent Literatures 1 to 3 below.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Laid-Open No. 2003-025916 -   Patent Literature 2: Japanese Patent Laid-Open No. 8-164796 -   Patent Literature 3: Japanese Patent Laid-Open No, 2008-155804

SUMMARY OF INVENTION Technical Problem

Shaft outside-fitting gears made of metal have problems of high manufacturing cost and heavy weight. In order to solve these problems, it is conceivable that a shaft outside-fitting gear is formed using a material including a resin as a base material (e.g., general resin or reinforced resin). However, forming a shaft outside-fitting gear using a material including a resin as a base material causes a problem in strength of the shaft outside-fitting gear.

This invention is intended to solve the problem in strength that occurs as a result of forming a shaft outside-fitting gear using a material including a resin as a base material.

Solution to Problem

An electric retractable view device for a vehicle according to this invention includes: a shaft attached to a vehicle body side; a rotating body supported by the shaft so as to be rotatable in a direction around an axis of the shaft; a motor mounted in the rotating body; and a power transmission mechanism including a shaft outside-fitting gear fitted on an outer circumference of the shaft so as to be rotatable in the direction around the axis of the shaft and a clutch mechanism that locks rotation, in the direction around the axis of the shaft, of the shaft outside-fitting gear via a spring force and cancels the locking via an external force against the spring force to allow the rotation, and the clutch mechanism includes a shaft outside-fitting gear-side clutch surface and a shaft-side clutch surface each including a clutch crest and a clutch valley that are arranged in the direction around the axis of the shaft and, upon a fitting force being provided by the spring force, are fitted to each other, the power transmission mechanism transmits a driving force of the motor to the shaft via the shaft outside-fitting gear and the clutch mechanism brought in the fitted state by the spring force, to rotate the rotating body in the direction around the axis of the shaft and thereby rotate a view device rotating section to which the rotating body is attached, in the direction around the axis of the shaft, the shaft outside-fitting gear is formed of a material including a resin as a base material, the shaft outside-fitting gear includes the shaft outside-fitting gear-side clutch surface in one end face in an axis direction of the shaft outside-fitting gear, the shaft outside-fitting gear-side clutch surface is disposed on an inner circumferential side and an outer circumferential side of a radial position of a tooth bottom of a gear tooth of the shaft outside-fitting gear relative to the radial position of the tooth bottom, in a radial direction of the shaft outside-fitting gear, and the one end face in the axis direction of the shaft outside-fitting gear has a structure in which a valley of the gear tooth of the shaft outside-fitting gear is occluded at least at a radial region at which the shaft outside-fitting gear-side clutch surface is disposed. Accordingly, since the shaft outside-fitting gear-side clutch surface is disposed on the inner circumferential side and the outer circumferential side of the radial position of the tooth bottom of the gear tooth of the shaft outside-fitting gear relative to the radial position of the tooth bottom, the shaft outside-fitting gear-side clutch surface can be disposed so as to be wide in the radial direction of the shaft outside-fitting gear, compared to a case where the shaft outside-fitting gear-side clutch surface is disposed only on the inner circumferential side of the radial position of the tooth bottom of the gear tooth of the shaft outside-fitting gear relative to the radial position of the tooth bottom. Accordingly, a force received by the shaft outside-fitting gear-side clutch surface can be dispersed in the radial direction of the shaft outside-fitting gear, and as a result, a strength of the shaft outside-fitting gear-side clutch surface can be enhanced. Therefore, the shaft outside-fitting gear-side clutch surface has a strength that is necessary as a component of a clutch mechanism for an electric retractable view device for a vehicle while the shaft outside-fitting gear-side clutch surface is formed of a material containing a resin as a base material. Also, since the shaft outside-fitting gear-side clutch surface is disposed on the structure in which the valley of the gear tooth is occluded, when the shaft outside-fitting gear-side clutch surface and the shaft-side clutch surface rotate relative to each other, the shaft-side clutch surface is prevented from hitting the gear tooth. Therefore, the relative rotation is prevented from being stuck and the gear tooth is prevented from being chipped. Also, since the shaft outside-fitting gear-side clutch surface is disposed on the structure in which the valley of the gear tooth is occluded, the shaft outside-fitting gear-side clutch surface can firmly be disposed on the shaft outside-fitting gear. Also, the gear tooth of the shaft outside-fitting gear is reinforced by the structure in which the valley of the gear tooth is occluded at the one end in the axis direction of the shaft outside-fitting gear, enabling enhancement in strength of the gear tooth.

In the electric retractable view device for a vehicle according to this invention, it is possible that the one end face in the axis direction of the shaft outside-fitting gear has a structure in which the valley of the gear tooth of the shaft outside-fitting gear is occluded at all of radial positions from the tooth bottom to a tooth tip. Accordingly, since the one end face in the axis direction of the shaft outside-fitting gear has the structure in which the valley of the gear tooth is occluded at all of radial positions from the tooth bottom to the tooth tip, at the time of resin molding of the shaft outside-fitting gear, the shaft outside-fitting gear can be resin-molded without making an end of a gear teeth-forming part of one molding die butt the other molding die. Consequently, at the time of the resin molding, breakage of the end of the gear teeth-forming part of the one molding die can be prevented.

In the electric retractable view device for a vehicle according to this invention, it is possible that the shaft outside-fitting gear-side clutch surface is disposed so as to reach a radial position of a tooth tip of the gear tooth in the radial direction of the shaft outside-fitting gear. Accordingly, the shaft outside-fitting gear-side clutch surface can be disposed so as to be very wide in the radial direction of the shaft outside-fitting gear. Consequently, the force received by the shaft outside-fitting gear-side clutch surface can widely be dispersed in the radial direction of the shaft outside-fitting gear, and as a result, the strength of the shaft outside-fitting gear-side clutch surface can be enhanced.

In the electric retractable view device for a vehicle according to this invention, it is possible that another end face in the axis direction of the shaft outside-fitting gear has a structure in which the valley of the gear tooth opens at all of radial positions from the tooth bottom to a tooth tip. Accordingly, when the shaft outside-fitting gear is fitted onto the shaft after a gear to be engaged with the shaft outside-fitting gear is incorporated into the electric retractable view device for a vehicle or when the gear (gear to be engaged with the shaft outside-fitting gear) is incorporated into the electric retractable view device for a vehicle after the shaft outside-fitting gear is fitted onto the shaft, both gears can be engaged with each other by causing a gear tooth of the gear (gear to be engaged with the shaft outside-fitting gear) to enter the valley of the gear tooth that opens to the other end face of the shaft outside-fitting gear.

In the electric retractable view device for a vehicle according to this invention, it is possible that a module of the shaft outside-fitting gear is not less than 0.6 and less than 1.0. Accordingly, since the module of the shaft outside-fitting gear is not less than 0.6, the shaft outside-fitting gear can have a strength that is necessary as a shaft outside-fitting gear for an electric retractable view device for a vehicle while the shaft outside-fitting gear is formed of a material including a resin as a base material. Also, since the module of the shaft outside-fitting gear is less than 1.0, it is possible to avoid an excessive increase in diameter of the shaft outside-fitting gear and an accompanying increase in size of the electric retractable view device for a vehicle.

In the electric retractable view device for a vehicle according to this invention, it is possible that: the clutch mechanism includes a clutch plate fitted on the outer circumference of the shaft; the clutch plate is formed of a material including a resin as a base material; the clutch plate includes a hollow to which the shaft is inserted, the shaft-side clutch surface is formed on an outer circumferential side of the clutch plate relative to the hollow; the shaft and the clutch plate each include a rotation preventing recess and a rotation preventing projection, in an outer circumferential surface of the shaft and an inner circumferential surface of the hollow of the clutch plate, respectively, the rotation preventing recesses and the rotation preventing projections being fitted to each other and thereby making the clutch plate movable in the axis direction of the shaft and unmovable in the direction around the axis; and the rotation preventing projection on the clutch plate side is formed so as to reach a position beyond a top of the clutch crest of the clutch plate in the axis direction of the clutch plate. Accordingly, since a length in the axis direction of the rotation preventing projection on the clutch plate side can be made to be long compared to a case where the rotation preventing projection on the clutch plate side is configured only up to a position that is the same as the top of the clutch crest of the clutch plate or a position below the top in the axis direction of the clutch plate, a force of the clutch plate holding the shaft can be enhanced.

In the electric retractable view device for a vehicle according to this invention, it is possible that: the clutch plate includes a barrel formed so as to reach the position beyond the top of the clutch crest in the axis direction of the clutch plate; in a center of a surface of the clutch plate as viewed in an axis direction of the clutch plate; an inner space of the barrel forms a part in an axis direction of the hollow of the clutch plate; a part of the rotation preventing projection on the clutch plate side, the part being formed at the position beyond the top of the clutch crest, is included in an inner circumferential surface of the barrel; and the shaft outside-fitting gear includes a barrel bearing in an inner circumferential surface of a hollow to which the shaft is inserted, the barrel bearing receiving the barrel in such a manner that the barrel is rotatable relative to the barrel bearing. Accordingly, since the part of the rotation preventing projection on the clutch plate side, the part being formed at the position beyond the top of the clutch crest is supported by the inner circumferential surface of the barrel, strength of the rotation preventing projection of the clutch plate can be ensured while a general thickness of the clutch plate (plate thickness except the barrel) is suppressed to be small. Also, since the barrel of the clutch plate is received on the barrel bearing of the shaft outside-fitting gear, a total thickness of the shaft outside-fitting gear and the clutch plate in a state in which the clutch crests and the clutch valleys of the shaft outside-fitting gear and the clutch plate are fitted together can be made to be small.

In an electric retractable view device for a vehicle according to this invention, it is possible that the rotation preventing projection of the clutch plate is disposed at a position at which the rotation preventing projection overlaps the clutch crest of the clutch plate in a circumferential direction of the clutch plate. Accordingly, since the rotation preventing projection of the clutch plate is disposed at the circumferential position at which the clutch plate is made thick by the clutch crest, stiffness of the rotation preventing projection can be enhanced.

In the electric retractable view device for a vehicle according to this invention, it is possible that either or each of a component providing the shaft outside-fitting gear-side clutch surface and a component providing the shaft-side clutch surface includes a lightening hole in a top of the relevant clutch crest. Accordingly, as a result of forming the lightening hole in the top of the clutch crest, which is a part that have no effect on clutch fitting, where the component providing the shaft outside-fitting gear-side clutch surface and/or the component providing the shaft-side clutch surface is molded using a material including a resin as a base material, weight of the component(s) can be reduced while generation of sink marks accompanying resin molding is suppressed. Also, a draft angle of a part of (each) molding die for resin molding of the component (s), the part allowing formation of the lightening hole, is set as around zero, enabling such part of the molding die to function as a “sticking” preventing structure when the molded product is released from the opposite molding die.

In the electric retractable view device for a vehicle according to this invention, it is possible that either or each of a component providing the shaft outside-fitting gear-side clutch surface and a component providing the shaft-side clutch surface includes a lightening hole in a bottom of the relevant clutch valley. Accordingly, as a result of forming the lightening hole in the bottom of the clutch valley, which is a part that have no effect on clutch fitting, where the component providing the shaft outside-fitting gear-side clutch surface and/or the component providing the shaft-side clutch surface is molded using a material including a resin as a base material, weight of the component (s) can be reduced while generation of sink marks accompanying resin molding is suppressed. Also, a draft angle of a part of (each) molding die for resin molding of the component (s), the part allowing formation of the lightening hole, is set as around zero, enabling such part of the molding die to function as a “sticking” preventing structure when the molded product is released from the opposite molding die.

A shaft outside-fitting gear according to this invention is a shaft outside-fitting gear to be incorporated in an electric retractable view device for a vehicle, wherein: the shaft outside-fitting gear is formed of a material including a resin as a base material; the shaft outside-fitting gear includes a shaft outside-fitting gear-side clutch surface in one end face in an axis direction of the shaft outside-fitting gear; the shaft outside-fitting gear-side clutch surface is disposed on an inner circumferential side and an outer circumferential side of a radial position of a tooth bottom of a gear tooth of the shaft outside-fitting gear relative to the radial position of the tooth bottom, in a radial direction of the shaft outside-fitting gear; and the one end face in the axis direction of the shaft outside-fitting gear has a structure in which a valley of the gear tooth of the shaft outside-fitting gear is occluded at least at a radial region at which the shaft outside-fitting gear-side clutch surface is disposed. Accordingly, since the shaft outside-fitting gear-side clutch surface is disposed on the inner circumferential side and the outer circumferential side of the radial position of the tooth bottom of the gear tooth of the shaft outside-fitting gear relative to the radial position of the tooth bottom, the shaft outside-fitting gear-side clutch surface can be disposed so as to be wide in the radial direction of the shaft outside-fitting gear, compared to a case where the shaft outside-fitting gear-side clutch surface is disposed only on the inner circumferential side of the radial position of the tooth bottom of the gear tooth of the shaft outside-fitting gear relative to the radial position of the tooth bottom. Accordingly, a force received by the shaft outside-fitting gear-side clutch surface can be dispersed in the radial direction of the shaft outside-fitting gear, and as a result, strength of the shaft outside-fitting gear-side clutch surface can be enhanced. Therefore, the shaft outside-fitting gear-side clutch surface has a strength that is necessary as a component of a clutch mechanism for an electric retractable view device for a vehicle while the shaft outside-fitting gear-side clutch surface is formed of a material containing a resin as a base material. Also, since the shaft outside-fitting gear-side clutch surface is disposed on the structure in which the valley of the gear tooth is occluded, when the shaft outside-fitting gear-side clutch surface and the shaft-side clutch surface rotate relative to each other, the shaft-side clutch surface is prevented from hitting the gear tooth. Therefore, the relative rotation is prevented from being stuck and the gear tooth is prevented from being chipped. Also, since the shaft outside-fitting gear-side clutch surface is disposed on the structure in which the valley of the gear tooth is occluded, the shaft outside-fitting gear-side clutch surface can firmly be disposed on the shaft outside-fitting gear. Also, the gear tooth of the shaft outside-fitting gear is reinforced by the structure in which the valley of the gear tooth is occluded at the one end in the axis direction of the shaft outside-fitting gear, enabling enhancement in strength of the gear tooth.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an assembled state of the door mirror in FIG. 2, and is a diagram of an end face cut at the position indicated by arrows C-C in FIG. 10.

FIG. 2 is an exploded perspective view of an electric retractable door mirror for the right side of a vehicle according to an embodiment of this invention.

FIG. 3 is an exploded perspective view of the electric retracting unit 16 illustrated in FIG. 2.

FIG. 4 is a perspective view of the shaft outside-fitting gear 54 illustrated in FIG. 3.

FIG. 5 is a plan view of the shaft outside-fitting gear 54 illustrated in FIG. 3.

FIG. 6 is a diagram of an end face cut at the position indicated by arrows A-A in FIG. 5.

FIG. 7 is a perspective diagram of the clutch plate 58 illustrated in FIG. 3 as viewed from the bottom side.

FIG. 8 is a bottom view of the clutch plate 58 illustrated in FIG. 3.

FIG. 9 is a diagram of an end face cut at the position indicated by arrows B-B in FIG. 8.

FIG. 10 is a plan view illustrating an assembled state of the door mirror in FIG. 2.

FIG. 11 is a perspective view of the frame 36 illustrated in FIG. 3 as viewed from the bottom side.

FIG. 12 is a plan view of the frame 36 illustrated in FIG. 3.

DESCRIPTION OF EMBODIMENT

An embodiment of this invention will be described. FIG. 2 is an exploded perspective view of an electric retractable door mirror for the right side of a vehicle, to which this invention is applied. FIG. 2 illustrates a state of a mirror rotating section (view device rotating section) 15 in an extended position as viewed from the back side (vehicle front side). Also, in FIG. 2, illustration of, e.g., a mirror surface adjustment actuator and a mirror plate both disposed in a front opening 14 a of a visor 14 and a housing cover (reference numeral 17 in FIG. 1) fitted on the back side of the visor 14 is omitted. This door mirror 10 includes a mirror base 12, a mirror rotating section 15, and an electric retracting unit 16 connected between the mirror base 12 and the mirror rotating section 15. The mirror rotating section 15 includes the visor 14. The mirror base 12 is provided so as to protrude from a vehicle body (right door) 13 to the right of the vehicle. The electric retracting unit 16 includes a fixed body 16 a in a lower part and a rotating body 16 b in an upper part. The rotating body 16 b is rotatable relative to the fixed body 16 a in a direction around a rotation axis 18. The rotating body 16 b of the electric retracting unit 16 is fixed to the back side of the visor 14 by screwing two screws 20 into the rotating body 16 b of the electric retracting unit 16 from a lower surface of the visor 14. In a state in which the rotating body 16 b is fixed to the visor 14, the fixed body 16 a of the electric retracting unit 16 is fixed to the mirror base 12 by screwing three screws 22 into the fixed body 16 a of the electric retracting unit 16 from a lower surface of the mirror base 12. Consequently, the mirror rotating section 15 including the visor 14 is attached to and thereby supported on the mirror base 12 via the electric retracting unit 16 so as to be rotatable in the direction around the rotation axis 18. The housing cover (reference numeral 17 in FIG. 1) not illustrated in FIG. 2 is fitted to a back surface of the visor 14. Consequently, an opening 14 b in the back surface of the visor 14 is occluded by the housing cover 17, and as a result, the electric retracting unit 16 is housed in a space surrounded by the visor 14 and the housing cover 17. The mirror rotating section 15 rotates upon being electrically driven by the electric retracting unit 16 and is movable alternatively to a retracted position and the extended position. Also, the mirror rotating section 15 is movable from the retracted position to a forward-tilted position through the extended position and vice versa upon being rotated by an external force.

An overall configuration of the inside of the electric retracting unit 16 will be described mainly with reference to FIG. 3. All of the components in FIG. 3 are detachably assembled into the electric retracting unit 16. The electric retracting unit 16 includes a shaft 24 forming the fixed body 16 a. The shaft 24 is formed of an integrally-molded product of a reinforced resin such as PA+GF resin (glass fiber-reinforced polyamide resin). The shaft 24 coaxially includes a shaft base 24 a having a large diameter and a disk-like shape in a lower part and a shaft axle 24 b having a small diameter and a cylindrical shape in an upper part. The shaft 24 is provided upright so as to be orthogonal to the mirror base 12 by fixing a lower surface of the shaft base 24 a to the mirror base 12 via the screws 22 (FIG. 2). A crest-valley repeated shape 26 is formed at an outermost circumferential position in an upper surface of the shaft base 24 a. The crest-valley repeated shape 26 is formed of three sets of a crest 26 b and a valley 26 a alternately arranged in a direction around the axis of the shaft 24, the sets being each arranged with an angle of 120 degrees. A circumferential length (angle) of one valley 26 a is longer than a circumferential length (angle) of one crest 26 b. Also, two height maintaining protrusions 28 are formed at respective innermost circumferential positions in the upper surface of the shaft base 24 a. These two height maintaining protrusions 28 are disposed so as to be spaced 180 degrees in the direction around the axis of the shaft 24 from each other and are connected to an outer circumferential surface of the shaft axle 24 b. Top surfaces of the height maintaining protrusions 28 and top surfaces of height maintaining protrusions 41 of a later-described frame 36 are in abutment with and slide on each other when the mirror rotating section 15 is moved from the extended position toward the forward-tilted position by an external force. The abutment and sliding between the top surfaces causes the height maintaining protrusions 28 to maintain a height of the frame 36 relative to the shaft 24 and thereby enable the mirror rotating section 15 to be electrically returned from the forward-tilted position to the extended position. Also, a bearing surface 30 is formed at a radial position between the crest-valley repeated shape 26 at the outermost circumferential position and the height maintaining protrusions 28 at the innermost circumferential position in the upper surface of the shaft base 24 a. The bearing surface 30 is formed so as to have a groove shape having a constant width, have an annular shape in the direction around the axis of the shaft 24 and be flat. A resin washer 34 is placed and received in the groove of the bearing surface 30. A hollow 31 of the shaft axle 24 b is provided so as to extend through the shaft base 24 a. A non-illustrated wire harness that supplies electric power to, e.g., the electric retracting unit 16 and the mirror surface adjustment actuator is inserted through the hollow 31. A rotation preventing shape 32 is formed at the outer circumferential surface of the shaft axle 24 b. The rotation preventing shape 32 includes five sets of a rotation preventing recess 32 a and a rotation preventing projection 32 b arranged alternately circumferentially, the sets being each arranged with a same circumferential length. The respective rotation preventing recesses 32 a and the respective rotation preventing projections 32 b are configured so as to extend in the axis direction of the shaft 24. An upper end of each rotation preventing recess 32 a opens upward in order to allow entry of a corresponding rotation preventing projection (a rotation preventing projection 62 b formed on an inner circumferential surface of a later-described clutch plate 58) to be fitted in the rotation preventing recess 32 a. In an outer circumferential surface of an upper part of the shaft axle 24 b, grooves 35 for allowing a later-described metal plate 66 to be put onto the upper part of the shaft axle 24 b and to be rotated and to be held at the upper part of the shaft axle 24 b are formed.

The frame 36 of the rotating body 16 b is rotatably supported on the shaft 24. The frame 36 is formed of an integrally-molded product of a reinforced resin such as PA+GF resin. The frame 36 includes an inner space 38 that opens upward. At a bottom surface 38 a of the inner space 38, a cylinder 40 is provided upright. A hollow 43 of the cylinder 40 extends through the bottom surface 38 a. Here, the referenced drawing will temporarily be moved from FIG. 3 to FIG. 11 to describe a configuration of a lower surface of the frame 36. On the lower surface of the frame 36, a cylinder 39 is provided so as to protrude downward (upward in FIG. 11). The cylinder 39 is disposed coaxially with the cylinder 40. Also, the cylinder 39 is larger in diameter and thickness than the cylinder 40. On an inner circumferential surface of the cylinder 39, two height maintaining protrusions 41 are formed. These two height maintaining protrusions 41 are disposed so as to be spaced 180 degrees in a direction around an axis of the cylinder 39 from each other and are connected to the inner circumferential surface of the cylinder 39. The top surfaces of the two height maintaining protrusions 41 and the top surfaces of the two height maintaining protrusions 28 (FIG. 3) of the shaft base 24 a are in abutment with and slide on each other. An inner circumferential surface of each height maintaining protrusion 41 is located at a same radial position as the inner circumferential surface 40 a of the cylinder 40, and both inner circumferential surfaces form a continuous surface. The height maintaining protrusions 28, 41 are located at a same radial position. A lower end face of the cylinder 39 forms a bearing surface 45 that faces the bearing surface 30 of the shaft 24. On the outer side of the cylinder 39, an outer barrel 49 is disposed coaxially with the cylinder 39 with a void 47 therebetween. Inside the void 47, a crest-valley repeated shape 27 to be fitted to the crest-valley repeated shape 26 (FIG. 3) in the upper surface of the shaft base 24 a is formed. The crest-valley repeated shape 27 is formed of three sets of a crest 27 b and a valley 27 a alternately arranged in the direction around the axis of the cylinder 39, the sets being each arranged with an angle of 120 degrees. A circumferential length (angle) of one valley 27 a is longer than a circumferential length (angle) of one crest 27 b. Each crest 27 b is disposed so as to be connected to an outer circumferential surface of the cylinder 39, an inner circumferential surface of the outer barrel 49 and a bottom surface of the void 47. In a partial circumferential area of the outer barrel 49, a stopper 51 is formed so as to protrude downward (upward in FIG. 11). The stopper 51 is inserted to a stopper groove 57 (FIG. 2) formed in the mirror base 12 so as to be movable circumferentially, and thus sets a maximum rotation range (from the retracted position to the forward-tilted position) of the mirror rotating section 15. The shaft axle 24 b is inserted to a continuous hollow 43 of the cylinders 39, 40 of the frame 36 from the cylinder 39 side. At this time, the bearing surface 45 of the frame 36 is bearing-supported by the bearing surface 30 of the shaft 24 with the resin washer 34 therebetween. Also, the inner circumferential surface 40 a of the cylinder 40 on the upper side is rotatably supported by the shaft axle 24 b. Consequently, the frame 36 is supported by the shaft 24 so as to be rotatable in the direction around the axis of the shaft 24. The crests 26 b of the crest-valley repeated shape 26 of the shaft 24 enter the void 47 in a bottom of the frame 36. In this state, the crest-valley repeated shape 26 and the crest-valley repeated shape 27 fitted together so as to be slidable on each other in both rotation directions within a predetermined angle range. In other words, the crest-valley repeated shape 26 and the crest-valley repeated shape 27 can slide on each other in both rotation directions until an inclined surface of a boundary between each crest 26 b and the corresponding valley 26 a and an inclined surface of a boundary between each crest 27 b and the corresponding valley 27 a are brought into abutment with and thereby locked by each other (or, in the retracting direction, until the stopper 51 is locked by one end of the stopper groove 57). This sliding allows the mirror rotating section 15 (FIG. 2) to rotate between the retracted position and the extended position. Also, when an external force directed to the front side of the vehicle, the external force having a predetermined value or more, is applied to the mirror rotating section 15 in the extended position, the crests 26 b and the crests 27 b mutually slide up on the inclined surfaces of the respective opposite crests against a biasing force of a later-described coil spring 64 and move onto the top surfaces of the respective opposite crests, whereby the fit between the crest-valley repeated shape 26 and the crest-valley repeated shape 27 is cancelled. The cancellation of the fit allows the mirror rotating section 15 to rotate to the forward-tilted position. On one side of the frame 36, screw through holes 46 for screw-fastening and thereby fixing the frame 36 to bosses 44 (FIG. 2) provided at two, upper and lower, positions in the back surface of the visor 14 are formed. In this embodiment, the screw through holes 46 are provided at three, upper, intermediate and lower, positions. From among the screw through holes 46, screws (not illustrated) are inserted to the screw through holes 46 at the two, upper and lower, positions and screwed into the bosses 44 at the two, upper and lower, positions, whereby the frame 36 is fixed to the back surface of the visor 14.

Referring back to FIG. 3, a resin washer 48 is loosely fitted on an outer circumference of the cylinder 40 in the inner space 38 of the frame 36. The resin washer 48 is placed and supported on the bottom surface 38 a of the inner space 38. The resin washer 48 is a product that is the same as the resin washer 34. An axle 52 a of a metal worm 52 is inserted to a resin worm wheel 50, whereby the worm wheel 50 and the worm 52 are assembled to each other so as to be unrotatable relative to each other. The assembled worm wheel 50 and worm 52 are put in the inner space 38 of the frame 36 and disposed at a predetermined position. At this time, lower surfaces of opposite ends 52 b, 52 c of the axle 52 a of the worm 52 are placed and supported on bearings (reference numerals 38 b, 38 c in FIG. 12) in the inner space 38. Consequently, the worm wheel 50 and the worm 52 can rotate integrally in the inner space 38. A shaft outside-fitting gear 54 is rotatably fitted on the outer circumference of the cylinder 40 in the inner space 38 of the frame 36. The shaft outside-fitting gear 54 is formed of an integrally-molded product of a reinforced resin such as PA+GF resin. A hollow 55 is formed in a center of a surface of the shaft outside-fitting gear 54 as viewed in an axis direction of the shaft outside-fitting gear 54. The cylinder 40 of the frame 36 and the shaft axle 24 b are rotatably inserted to the hollow 55. A bearing surface 106 (FIG. 6) in a lower surface of the shaft outside-fitting gear 54 is slidably placed and supported on the resin washer 48 (FIG. 1). At an outer circumferential surface of the shaft outside-fitting gear 54, gear teeth 54 b of a helical gear are formed. Consequently, the shaft outside-fitting gear 54 forms a worm wheel. The gear teeth 54 b engage with the worm 52. Consequently, the shaft outside-fitting gear 54 and the worm 52 form a worm gear. A shaft outside-fitting gear-side clutch surface 56 is formed at an upper surface of the shaft outside-fitting gear 54. The shaft outside-fitting gear-side clutch surface 56 is formed of five sets of a clutch valley 56 a and a clutch crest 56 b arranged alternately in a direction around an axis of the shaft outside-fitting gear 54, the sets being each arranged with a same circumferential length. A circumferential length (angle) of one clutch valley 56 a and a circumferential length (angle) of one clutch crest 56 b are set to be equal to each other.

The clutch plate 58 is put onto the shaft axle 24 b. Consequently, the clutch plate 58 is placed and supported on the shaft outside-fitting gear 54 concentrically with the shaft outside-fitting gear 54. The clutch plate 58 is formed of an integrally-molded product of a reinforced resin such as PA+GF resin. A hollow 59, to which the shaft axle 24 b is inserted so as to be unrotatable and movable axially, is formed in a center of a surface of the clutch plate 58 as viewed in an axis direction of the clutch plate 58. At a lower surface of the clutch plate 58, a shaft-side clutch surface 60 is formed. The shaft-side clutch surface 60 is formed of five sets of a clutch valley 60 a and a clutch crest 60 b arranged alternately in a direction around the axis of the clutch plate 58, the sets being each arranged with a same circumferential length. The shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 form a clutch mechanism 61. A circumferential length (angle) of one clutch valley 60 a and a circumferential length (angle) of one clutch crest 60 b of the shaft-side clutch surface 60 are set to be equal to each other. Also, the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 are equal to each other in inner diameter and outer diameter. Therefore, the clutch valleys 56 a and the clutch crests 56 b of the shaft outside-fitting gear-side clutch surface 56 are fitted to the clutch crests 60 b and the clutch valleys 60 a of the shaft-side clutch surface 60 with no backlash. A height changing part at a position of a boundary between each clutch valley 56 a and the relevant clutch crest 56 b and a height changing part at a position of a boundary between each clutch valley 60 a and the relevant clutch crest 60 b are formed of respective inclined surfaces, inclination angles of which are equal to each other. Consequently, the fit between the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 can be cancelled by means of a rotational force acting between these clutch surfaces 56, 60. A rotation preventing shape 62 is formed at an inner circumferential surface of the clutch plate 58. The rotation preventing shape 62 is formed of five sets of a rotation preventing recess 62 a and the rotation preventing projection 62 b that are arranged circumferentially and extend axially. The rotation preventing recesses 62 a and the rotation preventing projections 62 b face the rotation preventing projections 32 b and the rotation preventing recesses 32 a formed at the outer circumferential surface of the shaft axle 24 b, respectively, via a small gap. Consequently, the rotation preventing recesses 62 a and the rotation preventing projections 62 b are fitted to the rotation preventing projections 32 b and the rotation preventing recesses 32 a so as to be unrotatable in the direction around the axis and slidable axially. As a result, the clutch plate 58 is fitted on the shaft axle 24 b so as to be unrotatable in a direction around the axis of the shaft axle 24 b and movable axially.

The coil spring 64 is put on the shaft axle 24 b. Consequently, the coil spring 64 is placed and supported on the clutch plate 58 concentrically with the clutch plate 58. The metal plate 66 is disposed on the coil spring 64. The coil spring 64 is pressed and contracted by the metal plate 66, whereby the metal plate 66 is put onto the shaft axle 24 b. Protrusions 66 a formed at an inner circumferential surface of the metal plate 66 are inserted to the grooves 35 formed in the outer circumferential surface of the upper part of the shaft axle 24 b and the metal plate 66 is pressed downward, and next, the metal plate 66 is rotated, whereby the metal plate 66 is fitted to the upper part of the shaft axle 24 b. Consequently, the coil spring 64 is fitted in a contracted state to the shaft axle 24 b. At this time, an expansion force of the coil spring 64 acts between an upper surface of the clutch plate 58 and a lower surface of the metal plate 66. This expansion force provides a fitting force between the crest-valley repeated shape 26 at the upper surface of the shaft base 24 a and the crest-valley repeated shape 27 (FIG. 11) at the lower surface of the frame 36 and also between the shaft outside-fitting gear-side clutch surface 56 at the upper surface of the shaft outside-fitting gear 54 and the shaft-side clutch surface 60 at the lower surface of the clutch plate 58. However, when the mirror rotating section 15 is located between the retracted position and the extended position, the expansion force provided from the coil spring 64 to the frame 36 is received by the bearing surface 30 via the resin washer 34 through the bearing surface 45, and thus, rotation of the mirror rotating section 15 is performed by the bearing surfaces 45, 30 sliding on each other with the resin washer 34 therebetween. In other words, the rotation of the mirror rotating section 15 is bearing-supported by the abutment and sliding between the bearing surfaces 45, 30 with the resin washer 34 therebetween. Therefore, at this time, the opposed surfaces of the crest-valley repeated shapes 26, 27 are separated and are neither in abutment with nor slide on each other (see FIG. 1).

After assembly of all of the respective components illustrated on the right side of FIG. 3, an outer plate 68 is placed on a step 36 b on the inner circumferential side of an opening 36 a at an upper end of the frame 36 and then the opening 36 a is thus closed. The outer plate 68 is formed of an integrally-molded product of a resin such as POM (polyacetal). The outer plate 68 includes a barrel 72 and a dome 74 at an upper surface thereof. The barrel 72 receives and holds a motor 76. The dome 74 surrounds an upper part of the shaft axle 24 b, the upper part protruding upward from the opening 36 a of the frame 36, and the coil spring 64 and the metal plate 66. A circular hole 74 a that allows the upper part of the shaft axle 24 b to protrude therefrom is provided in a center of a surface of the dome 74 as viewed in an axis direction of the dome. Before the outer plate 68 is put on the frame 36, the motor 76 is inserted to the barrel 72 from above and the motor 76 is thus fitted to the outer plate 68. A motor shaft (rotation axis rod) 78 of the motor 76 protrudes vertically downward below the outer plate 68 through a hole 73 a formed in a center of a bottom 73 (FIG. 1) in the barrel 72. A worm 80 is fitted onto the motor shaft 78. In a state in which the outer plate 68 holds the motor 76 and the worm 80 in this way, the outer plate 68 is placed on the step 36 b on the inner circumferential side of the opening 36 a of the frame 36. At this time, the worm 80 and the worm wheel 50 engage with each other and form a worm gear. Also, the worm 80, the worm wheel 50, the worm 52, the shaft outside-fitting gear 54 and the clutch plate 58 form a power transmission mechanism 81 that transmits a driving force of the motor 76 to the shaft axle 24 b. Also, at a lower surface of the outer plate 68, two protruding pieces 77 are formed so as to protrude downward from the lower surface. In FIG. 3, only the near-side protruding piece 77 of the two protruding pieces 77 is shown. The other protruding piece 77 is located on the side diagonally opposed to the near-side protruding piece 77. Lower end faces of the two protruding pieces 77 face upper surfaces of the opposite ends 52 b, 52 c of the axle 52 a of the worm 52 via a small gap, respectively, whereby upward movement of the worm 52 and the worm wheel 50 is restricted. After the placement of the outer plate 68 on the step 36 b on the inner circumferential side of the opening 36 a of the frame 36, the outer plate 68 is fixed to the frame 36 via two screws 82.

A configuration of the inside of the inner space 38 of the frame 36 will be described with reference to FIG. 12. Inside the inner space 38 of the frame 36, in addition to the components already described, e.g., a worm wheel receiving space 111, a worm receiving space 113, a worm wheel entry port 115 and two screw holes 117 are formed. The worm wheel receiving space 111 receives the worm wheel 50 coaxially fixed and fitted to the axle 52 a of the worm 52. At this time, the opposite ends 52 b, 52 c of the axle 52 a of the worm 52 are supported on the bearings 38 b, 38 c. The worm receiving space 113 is a space that coaxially receives the worm 80, and is formed of a space having a circular column shape having a diameter that is larger than that of the worm 80. The worm wheel entry port 115 causes the worm wheel receiving space 111 and the worm receiving space 113 to communicate with each other. Consequently, the worm wheel entry port 115 causes an outer circumferential surface of the worm wheel 50 to enter the worm receiving space 113 through the worm wheel entry port 115. As a result, the worm wheel 50 and the worm 80 engage with each other. The two screw holes 117 are screw holes for screw-in of the two screws 82 (FIG. 3) for fixing the outer plate 68 to the frame 36. A bearing recess 93 having a diameter that is smaller than a general diameter of the worm receiving space 113 is formed in a bottom of the worm receiving space 113. Grease is charged in the bearing recess 93, and a distal end 80 a (FIGS. 1 and 3) of the worm 80 is received in the bearing recess 93. Consequently, the distal end 80 a of the worm 80 is bearing-supported in the bearing recess 93. At the lower surface of the outer plate 68, a circular projection 119 (FIG. 1) is formed concentrically with the hole 73 a (hole for letting the motor shaft 78 through, FIG. 1) in the lower surface of the outer plate 68. The projection 119 is received in a circular upper opening 113 a of the worm receiving space 113. At this time, the projection 119 is received in the upper opening 113 a with no gap (or with almost no gap) therearound except a part facing the worm wheel entry port 115. Consequently, an area that is no less than a half of an entire outer circumferential surface of the projection 119 is surrounded and supported by an inner circumferential surface of the upper opening 113 a. As a result, the motor shaft 78 protruding from the hole 73 a at a center of the projection 119 is positioned relative to the worm receiving space 113 in a surface direction perpendicular to an axis of the motor shaft 78. Around the worm receiving space 113, a cylindrical wall 121 having a constant thickness is provided, and a deep lightening hole 123 is provided outside the cylindrical wall 121. The lightening hole 123 is formed at a place excluding the part facing the worm wheel entry port 115, and consequently, the lightening hole 123 is formed in a C shape in plan view. The provision of the lightening hole 123 enables suppression of sink marks accompanying resin molding of the frame 36 and thus enables enhancement in molding accuracy of the upper opening 113 a of the worm receiving space 113. Consequently, an accuracy of positioning of the motor shaft 78 relative to the worm receiving space 113 in the surface direction perpendicular to the axis of the motor shaft 78 is improved. As a result, the engagement between the worm 80 and the worm wheel 50 is maintained in a normal state, enabling operating sound generated when the worm 80 and the worm wheel 50 rotate in engagement can be maintained at a normal level.

After the fixation of the outer plate 68 to the frame 36, a circuit board (printed board) 84 is disposed upright in a space 75, between the barrel 72 and the dome 74, of the upper surface of the outer plate 68. In the circuit board 84, a motor drive circuit, motor connection terminals 86 and a connector receiving tool 88 are mounted. The motor drive circuit supplies electric drive power to the motor 76. The motor connection terminals 86 interconnect the motor drive circuit and terminals of the motor 76. A connector at a distal end of the wire harness is inserted to the connector receiving tool 88, and as a result, the connector receiving tool 88 interconnects the wire harness and the motor drive circuit. A lower end 84 a of the circuit board 84 is inserted to a groove 75 a of the outer plate 68, the groove 75 a being formed in a bottom of the space 75 between the barrel 72 and the dome 74. Distal ends of the motor connection terminals 86 are inserted in the respective terminals of the motor 76. Consequently, the circuit board 84 is disposed upright in the space 75.

After the fixation of the outer plate 68 to the frame 36 and the attachment of the circuit board 84 to the outer plate 68, a seal cap 90 is put on the outer plate 68. The seal cap 90 is formed of an integrally-molded product of a resin such as PP (polypropylene). In an upper surface of the seal cap 90, a circular hole 92 that communicates with an upper opening 31 a of the hollow 31 of the shaft axle 24 b is provided. Also, in one side surface of the seal cap 90, a connector insertion port 94 that communicates with the connector receiving tool 88 of the circuit board 84 is provided. Also, at each of four positions around an opening 96 of a lower end of the seal cap 90, a claw locking frame 98 is formed. Upon the seal cap 90 being put on the outer plate 68 and the seal cap 90 being pushed down, claws 100 configured at four positions around an upper outer circumferential surface of the frame 36 so as to protrude therefrom engage with the respective claw locking frames 98 of the seal cap 90. Consequently, the frame 36 and the seal cap 90 are joined, whereby the electric retracting unit 16 is assembled in an integrated manner. The wire harness is inserted through the hollow 31 of the shaft axle 24 b of the electric retracting unit 16 assembled in this way. The wire harness includes a wiring for the electric retracting unit 16. In addition, the wire harness includes, e.g., a wiring for the mirror adjustment actuator and a wiring for a turn lamp depending on the functions included in the door mirror 10. An end on the mirror rotating section 15 side of the wire harness is drawn out from the circular hole 92 of the seal cap 90. An end on the vehicle body side of the wire harness is drawn out from a lower end of the hollow 31 of the shaft 24 and guided to the inside of the vehicle body. A connector is fitted to an end on the mirror rotating section 15 side of each wiring in the wire harness. From among the connectors, a connector 89 (FIG. 10) for a distal end of the wiring for the electric retracting unit 16 is inserted to the connector insertion port 94 and thereby connected to the connector receiving tool 88 of the circuit board 84.

Detailed configurations of the shaft outside-fitting gear 54 and the clutch plate 58 will be described. First, the shaft outside-fitting gear 54 will be described. FIGS. 4 to 6 illustrate a detailed configuration of the shaft outside-fitting gear 54. FIG. 4 is a perspective view of the shaft outside-fitting gear 54, FIG. 5 is a plan view of the same, and FIG. 6 is a diagram of an end face cut at the position indicated by arrows A-A in FIG. 5. The hollow 55 is formed in the center of the surface of the shaft outside-fitting gear 54 as viewed in the axis direction of the shaft outside-fitting gear 54. At the outer circumferential surface of the shaft outside-fitting gear 54, gear teeth (helical teeth) 54 b are formed. A module of the gear teeth 54 b of the shaft outside-fitting gear 54 is set as, for example, 0.85. Consequently, the module of the gear teeth 54 b of the shaft outside-fitting gear 54 is no less than 0.6, and thus, the shaft outside-fitting gear 54 can have a strength that is necessary as a shaft outside-fitting gear for an electric retracting unit while the shaft outside-fitting gear 54 is formed of a material including a resin as a base material. Also, the module of the gear teeth 54 b of the shaft outside-fitting gear 54 is less than 1.0, and thus, it is possible to avoid an excessive increase in diameter of the shaft outside-fitting gear 54 and an accompanying increase in size of the mirror rotating section 15 of the door mirror 10 due to an increase in size of the electric retracting unit 16. The shaft outside-fitting gear-side clutch surface 56 is formed at the upper surface of the shaft outside-fitting gear 54. The shaft outside-fitting gear-side clutch surface 56 is formed of the clutch valleys 56 a and the clutch crests 56 b disposed alternately in the direction around the axis of the shaft outside-fitting gear 54. As illustrated in FIG. 6, the shaft outside-fitting gear-side clutch surface 56 is disposed extending over the inner circumferential side and the outer circumferential side of a radial position of each tooth bottom P1 of the gear tooth 54 b relative to the radial position of the tooth bottom P1, in the radial direction of the shaft outside-fitting gear 54. In FIG. 6, a dimension W indicates a width, in the radial direction of the shaft outside-fitting gear 54, of the shaft outside-fitting gear-side clutch surface 56. Also, an outer circumferential end 56 c of the shaft outside-fitting gear-side clutch surface 56 is disposed so as to reach a radial position of a tooth tip P2 of each gear tooth 54 b (to be precise, at a position slightly on the outer circumferential side relative to the radial position of the tooth tip P2 of each gear tooth 54 b). The clutch valleys 56 a are disposed on a thin plate 53. Consequently, at one end, on the side on which the shaft outside-fitting gear-side clutch surface 56 is disposed, of the shaft outside-fitting gear 54, the valleys 54 a of the gear teeth 54 b are occluded at all of radial positions from the tooth bottom P1 to the tooth tip P2 (see FIGS. 5 and 6). In this way, the shaft outside-fitting gear-side clutch surface 56 is disposed so as to be wide in the radial direction of the shaft outside-fitting gear 54, and thus, a force received by the shaft outside-fitting gear-side clutch surface 56 can be dispersed in the radial direction of the shaft outside-fitting gear 54. Consequently, the shaft outside-fitting gear-side clutch surface 56 can have a high strength. Also, since the clutch valleys 56 a are disposed on the thin plate 53, when the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 rotate relative to each other, the shaft-side clutch surface 60 is prevented from hitting the gear teeth 54 b. Therefore, the relative rotation is prevented from being stuck and the gear teeth 54 b are prevented from being chipped. Also, since the shaft outside-fitting gear-side clutch surface 56 is disposed on the structure in which the valleys 54 a of the gear teeth 54 b are occluded, the shaft outside-fitting gear-side clutch surface 56 can firmly be disposed on the shaft outside-fitting gear 54. Also, the gear teeth 54 b of the shaft outside-fitting gear 54 are reinforced by the structure in which the valleys 54 a of the gear teeth 54 b are occluded at the one end in the axial direction of the shaft outside-fitting gear, enabling enhancement in strength of the gear teeth 54 b. Also, since the one end face in the axis direction of the shaft outside-fitting gear 54 has the structure in which the valleys 54 a of the gear teeth 54 b are occluded at all of the radial positions from the tooth bottom P1 to the tooth tip P2, at the time of resin molding of the shaft outside-fitting gear 54, the shaft outside-fitting gear 54 can be resin-molded without making an end of a gear teeth-forming part of one molding die butt the other molding die. Consequently, at the time of resin molding, breakage of the end of the gear-teeth forming part of the one molding die is prevented. Also, a lower surface 56 d of each clutch crest 56 b is disposed so as to be in plane with a lower surface 53 a of the thin plate 53. As a result, the gear teeth 54 b have a uniform width in the axis direction of the shaft outside-fitting gear 54 in the entire circumference.

In a top of each clutch crest 56 b, a lightening hole 102 is formed. Also, in a bottom of each clutch valley 56 a, a lightening hole 104 is formed at a position on the inner circumferential side relative to a dedendum circle of the gear teeth 54 b (that is, a position at which the lightening hole 104 does not interfere with the gear teeth 54 b). Consequently, generation of sink marks in the shaft outside-fitting gear 54 accompanying resin molding can be suppressed, and also weight of the shaft outside-fitting gear 54 can be reduced. Also, draft angles of parts of a molding die for resin molding of the shaft outside-fitting gear 54, the parts allowing formation of the lightening holes 102, 104, are set as around zero degrees, enabling such parts of the molding die to function as a “sticking” preventing structure when the shaft outside-fitting gear 54 is released from the opposite molding die.

At an inner circumferential surface of the hollow 55 of the shaft outside-fitting gear 54, a circular small-diameter part 55 a is formed at an intermediate position in a top-bottom direction of the inner circumferential surface. The small-diameter part 55 a faces the shaft axle 24 b with a small gap therebetween. At the inner circumferential surface of the hollow 55, a cylindrical barrel bearing 55 b having a diameter that is larger than that of the small-diameter part 55 a is formed on the upper side of the small-diameter part 55 a. A later-described barrel 108 of the clutch plate 58 is received on the barrel bearing 55 b. The clutch valleys 56 a and the clutch crests 56 b are formed so as to reach an inner circumferential surface of the barrel bearing 55 b on the inner circumferential side. At the inner circumferential surface of the hollow 55, a cylinder receiving portion 55 c is formed on the lower side of the small-diameter part 55 a. The cylinder 40 of the frame 36 is rotatably received on the cylinder receiving portion 55 c. At a radial position between an inner circumferential surface of the cylinder receiving portion 55 c and the dedendum circle of the gear teeth 54 b in the lower surface of the shaft outside-fitting gear 54, the bearing surface 106 is formed continuously through the entire circumference in the direction around the axis of the shaft outside-fitting gear 54. The bearing surface 106 is formed so as to protrude slightly below the gear teeth 54 b. The bearing surface 106 is slidably placed and supported on the resin washer 48 (FIG. 3). Consequently, the shaft outside-fitting gear 54 is slidably supported on the resin washer 48 inside the inner space 38 of the frame 36 and is supported by the cylinder 40 so as to be rotatable in the direction around the axis.

The lower surface of the shaft outside-fitting gear 54 has a structure in which the valleys 54 a of the gear teeth 54 b fully open to the lower surface. Therefore, the worm 52 and the gear teeth 54 b can be made to engage with each other by fitting the shaft outside-fitting gear 54 onto the shaft axle 24 b after putting the worm 52 in the inner space 38 of the frame 36 (FIG. 3).

Next, the clutch plate 58 will be described. FIGS. 7 to 9 illustrate a detailed configuration of the clutch plate 58. FIG. 7 is a perspective view of the clutch plate 58 as viewed from the bottom side, FIG. 8 is a bottom view of the same, and FIG. 9 is a diagram of an end face cut at the position indicated by arrow B-B in FIG. 8. The hollow 59 is formed in the center of the surface of the clutch plate 58 as viewed in the axis direction of the clutch plate 58. An outer diameter of the clutch plate 58 is set to be equal to an outer diameter of the shaft outside-fitting gear 54. At the lower surface (surface on the side shown in FIG. 7) of the clutch plate 58, the shaft-side clutch surface 60 is formed. The shaft-side clutch surface 60 is formed of the clutch valleys 60 a and the clutch crests 60 b arranged alternately in the direction around the axis of the clutch plate 58. The clutch valleys 60 a and the clutch crests 60 b are formed so as to reach an outermost position in the clutch plate 58 on an outer circumferential side.

In a center of the lower surface of the clutch plate 58, a cylindrical barrel 108 is formed so as to reach a position beyond tops of the clutch crests 60 b. The clutch valleys 60 a and the clutch crests 60 b are formed so as to reach an outer circumferential surface of the barrel 108 on the inner circumferential side, and inner circumferential ends of the clutch valleys 60 a and the clutch crests 60 b are connected to the outer circumferential surface of the barrel 108. The barrel 108 is rotatably received in the barrel bearing 55 b of the shaft outside-fitting gear 54. The hollow 59 formed in the center of the surface of the clutch plate 58 as viewed in the axis direction of the clutch plate 58 is formed continuously from the upper surface of the clutch plate 58 to a distal end of the barrel 108. The rotation preventing recesses 62 a and the rotation preventing projections 62 b of the rotation preventing shape 62 are formed at an inner circumferential surface of the hollow 59 over an entire length in an axis direction of the hollow 59 (entire length in a thickness direction of the clutch plate 58). The rotation preventing projections 62 b are disposed at respective positions at which the rotation preventing projections 62 b circumferentially overlap the clutch crests 60 b.

FIG. 10 illustrates a plan view of an assembled state of the door mirror 10 in FIG. 2 having the configuration described above. In FIG. 10, illustration of the housing cover 17 and the mirror base 12 is omitted. Also, the electric retracting unit 16 is illustrated with the seal cap 90 removed and the connector 89 at the distal end of the wire harness inserted to the connector receiving tool 88, rubber packing 101 being attached to the connector 89. Also, FIG. 1 illustrates an end face cut at the position indicated by arrow C-C in FIG. 10. FIG. 1 illustrates a state in which the housing cover 17 is fitted to the visor 14, the mirror rotating section 15 is in the extended position and the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 engage with each other. At this time, although it is not shown in FIG. 1, the inclined surfaces of the boundaries between the crests 26 b and the valleys 26 a and the relevant inclined surfaces of the boundaries between the crests 27 b and the valleys 27 a are in abutment with each other and whereby the crest-valley repeated shape 26 and the crest-valley repeated shape 27 are locked by each other. Rotational operation of the mirror rotating section 15 will be described based on FIG. 1.

«Normal Electric Retracting/Extending Operation»

In the state in FIG. 1, upon an instruction for retracting being provided by operating a mirror switch, the motor 76 is started. Consequently, the bearing surface 30 and the bearing surface 45 slide on each other with the resin washer 34 therebetween, and the bottom surface 38 a of the inner space 38 of the frame 36 and the bearing surface 106 of the lower surface of the shaft outside-fitting gear 54 slide on each other with the resin washer 48 therebetween, whereby the mirror rotating section 15 rotates in a retracting direction. Upon the rotation of the mirror rotating section 15 being physically stopped in the retracted position by engagement between the stopper 51 (FIG. 11) and the one end of stopper groove 57 (FIG. 2), the stoppage is detected and the driving of the motor 76 is stopped. Consequently, the mirror rotating section 15 is held in the retracted position. In this state, upon an instruction for extending being provided by operating the mirror switch, the motor 76 is started in a reverse direction, whereby the mirror rotating section 15 rotates in an extending direction. Upon the rotation of the mirror rotating section 15 being stopped in the extended position by engagement between the inclined surfaces of the boundaries between the crests 26 b and the valleys 26 a of the crest-valley repeated shape 26 and the inclined surfaces of the boundaries between the crests 27 b and the valleys 27 a of the crest-valley repeated shape 27, the stoppage is detected and the driving of the motor 76 is stopped. Consequently, the mirror rotating section 15 is held in the extended position.

«Manual Retracting/Extending Operation»

In the state in FIG. 1, upon a force being manually applied in the retracting direction to the mirror rotating section 15, the gear teeth 54 b engages with the worm 52 that is not rotated, and thus the shaft outside-fitting gear 54 is unrotatable relative to the frame 36, and thus, the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 are disengaged from each other against the biasing force of the coil spring 64. Consequently, the mirror rotating section 15 is rotated in the retracting direction. The rotation of the mirror rotating section 15 is physically stopped in the retracted position by engagement between the stopper 51 and the one end of the stopper groove 57. In this state, upon a force in the extending direction being manually applied to the mirror rotating section 15, the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 are disengaged from each other against the biasing force of the coil spring 64 as in the above, and thus, the mirror rotating section 15 is rotated in the extending direction. The rotation of the mirror rotating section 15 is stopped in the extended position by engagement between the crest-valley repeated shape 26 and the inclined surfaces of the boundaries between the crests 26 b and the valleys 26 a of the crest-valley repeated shape 27. At this time, the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 are brought back into engagement with each other.

«Forward Tilting Operation by External Force»

In the state in FIG. 1, upon an external force having a predetermined value or more, the external force being directed to the front side of the vehicle, being provided to the mirror rotating section 15, the crests 26 b and the crests 27 b of the crest-valley repeated shape 26 and the crest-valley repeated shape 27 move up on the relevant inclined surfaces against the biasing force of the coil spring 64, whereby the fit between the crest-valley repeated shape 26 and the crest-valley repeated shape 27 is cancelled. Consequently, the frame 36 is brought up relative to the shaft 24, and the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 are disengaged from each other against the biasing force of the coil spring 64, and the mirror rotating section 15 is thus rotated in a forward tilting direction. This rotation is initially performed by abutment and sliding between top surfaces of the crests 26 b and the crests 27 b. As the rotation advances, the abutment between the top surfaces of the crests 26 b and the crests 27 b is cancelled, and the crests 26 b and the crest 27 b try to move down on the respective opposite inclined surfaces mutually. However, before the crests 26 b and the crests 27 b run on the respective opposite inclined surfaces, the top surfaces of the height maintaining protrusions 28 and the height maintaining protrusion 41 are brought into abutment with and slide on each other. As a result, the height of the frame 36 relative to the shaft 24 is maintained. The mirror rotating section 15 is physically stopped in the forward-tilted position by engagement between the stopper 51 and another end of the stopper groove 57, with the height of the frame 36 still maintained.

«Electric Operation of Returning from Forward-Tilted Position»

In a state in which the mirror rotating section 15 is located in the forward-tilted position, upon an instruction for retracting being provided by operating the mirror switch, the motor 76 is started. At this time, the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 engage with each other again. Also, at this time, the height of the frame 36 relative to the shaft 24 is maintained by abutment between the top surfaces of the height maintaining protrusions 28, 41 (that is, the crests 26 b and the crests 27 b of the crest-valley repeated shape 26 and the crest-valley repeated shape 27 do not need to move up on the respective opposite inclined surfaces mutually), and thus, the mirror rotating section 15 rotates in the retracting direction. During the rotation, the abutment between the top surfaces of the height maintaining protrusions 28, 41 is cancelled and is taken over by abutment between the top surfaces of the crests 26 b and the crests 27 b. Upon the mirror rotating section 15 further rotating, the crests 26 b and the crests 27 b move down on the respective opposite inclined surfaces mutually, and the mirror rotating section 15 moves to the retracted position through the extended position and stops. Upon an instruction for extending being provided again by operating the mirror switch, the mirror rotating section 15 rotates to the extended position and stops by means of normal electric extending operation.

«Manual Operation of Returning from Forward-Tilted Position»

In a state in which the mirror rotating section 15 is located in the forward-tilted position, upon a force being manually applied to the mirror rotating section 15, the mirror rotating section 15 is rotated in the retracting direction with the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 disengaged. As the rotation advances, the crests 26 b and the crests 27 b move down on the respective opposite inclined surfaces mutually, and in the extended position, the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 engage with each other, and the rotation of the mirror rotating section 15 can thus be stopped. Upon a force being further applied to the mirror rotating section 15 in the retracting direction, the shaft outside-fitting gear-side clutch surface 56 and the shaft-side clutch surface 60 are disengaged from each other, and thus the mirror rotating section 15 is rotated in the retracting direction. The rotation of the mirror rotating section 15 is physically stopped in the retracted position by engagement between the stopper 51 and the one end of the stopper groove 57.

Although in the above-described embodiment, the shaft outside-fitting gear-side clutch surface 56 is disposed so as to reach the radial position of the tooth tips of the gear teeth 54 b, this invention is not limited to this case. In other words, the outer circumferential end of the shaft outside-fitting gear-side clutch surface 56 can also be disposed at an intermediate position between the tooth bottoms and the tooth tips of the gear teeth 54 b. Also, although in the above-described embodiment, the one end face in the axis direction of the shaft outside-fitting gear 54 has the structure in which the valleys of the gear teeth 54 b of the shaft outside-fitting gear 54 are occluded at all of the radial positions from the tooth bottom to the tooth tip, this invention is not limited to this case. In other words, if the shaft outside-fitting gear-side clutch surface 56 is disposed so as not to reach the radial position of the tooth tip of each gear tooth 54 b, the valleys of the gear teeth 54 b can be occluded only at a radial region at which the shaft outside-fitting gear-side clutch surface 56 exists. Also, although in the above-described embodiment, the valleys of the gear teeth 54 b of the shaft outside-fitting gear 54 are occluded only by the one end face in the axis direction of the shaft outside-fitting gear 54, this invention is not limited to this case. In other words, the valleys of the gear teeth 54 b of the shaft outside-fitting gear 54 can also be occluded by the opposite end faces in the axis direction of the shaft outside-fitting gear 54. Consequently, the strength of the gear teeth 54 b can further be enhanced. Also, although in the above embodiment, the gear teeth 54 b of the shaft outside-fitting gear 54 are helical teeth to be engaged with the worm 52, this invention is not limited to this case. In other words, the gear teeth 54 b of the shaft outside-fitting gear 54 can also be those of a spur gear to be engaged with a spur gear. Also, although in the above embodiment, the lightening holes 102 are formed in the respective tops of the clutch crests 56 b of the shaft outside-fitting gear 54 and the lightening holes 104 are formed in the respective bottoms of the clutch valleys 56 a, lightening grooves can be formed in tops of the clutch crests 60 b and tops of the clutch valleys 60 a of the clutch plate 58, respectively. Also, although the above embodiment has been described in terms of the case where this invention is applied to an electric retractable rear view mirror for a vehicle, this invention is not limited to this case. In other words, this invention is applicable to any of an electric retractable rear view camera for a vehicle, the rear view camera being mounted on a door of a vehicle so as to protrude to the lateral side of the vehicle, other electric retractable rear-view devices for a vehicle and electric retractable view devices for a vehicle for purposes other than a rear view purpose, instead of applying this invention to a door mirror. An electric retractable rear view camera for a vehicle can be formed as, for example, one obtained by forming the visor 14 in FIG. 2 so as to have a small size and, instead of the mirror plate, mounting a camera in the visor 14 in such a manner that an optical axis of the camera faces the rear side of the vehicle when the visor 14 is in a use position.

REFERENCE SIGNS LIST

-   10 . . . electric retractable door mirror (electric retractable view     device for vehicle), 13 . . . vehicle body, 15 . . . mirror rotating     section (view device rotating section), 16 . . . electric retracting     unit, 16 b . . . rotating body, 24 . . . shaft, 32 a, 62 a . . .     rotation preventing recess, 32 b, 62 b . . . rotation preventing     projection, 53 . . . thin plate, 54 . . . shaft outside-fitting     gear, 54 b . . . gear teeth, 55 b . . . barrel bearing, 56 . . .     shaft outside-fitting gear-side clutch surface, 56 a, 60 a . . .     clutch valley, 56 b, 60 b . . . clutch crest, 58 . . . clutch plate,     59 . . . hollow of clutch plate, 60 . . . shaft-side clutch surface,     61 . . . clutch mechanism, 64 . . . coil spring, 76 . . . motor, 81     . . . power transmission mechanism, 108 . . . barrel, 102, 104 . . .     lightening hole, P1 . . . tooth bottom, P2 . . . tooth tip 

1. An electric retractable view device for a vehicle, the view device comprising: a shaft attached to a vehicle body side; a rotating body supported by the shaft so as to be rotatable in a direction around an axis of the shaft; a motor mounted in the rotating body; and a power transmission mechanism including a shaft outside-fitting gear fitted on an outer circumference of the shaft so as to be rotatable in the direction around the axis of the shaft and a clutch mechanism that locks rotation, in the direction around the axis of the shaft, of the shaft outside-fitting gear via a spring force and cancels the locking via an external force against the spring force to allow the rotation, wherein the clutch mechanism includes a shaft outside-fitting gear-side clutch surface and a shaft-side clutch surface each including a clutch crest and a clutch valley that are arranged in the direction around the axis of the shaft and, upon a fitting force being provided by the spring force, are fitted to each other, the power transmission mechanism transmits a driving force of the motor to the shaft via the shaft outside-fitting gear and the clutch mechanism brought in the fitted state by the spring force, to rotate the rotating body in the direction around the axis of the shaft and thereby rotate a view device rotating section to which the rotating body is attached, in the direction around the axis of the shaft, the shaft outside-fitting gear is formed of a material including a resin as a base material, the shaft outside-fitting gear includes the shaft outside-fitting gear-side clutch surface in one end face in an axis direction of the shaft outside-fitting gear, the shaft outside-fitting gear-side clutch surface is disposed on an inner circumferential side and an outer circumferential side of a radial position of a tooth bottom of a gear tooth of the shaft outside-fitting gear relative to the radial position of the tooth bottom, in a radial direction of the shaft outside-fitting gear, and the one end face in the axis direction of the shaft outside-fitting gear has a structure in which a valley of the gear tooth of the shaft outside-fitting gear is occluded at least at a radial region at which the shaft outside-fitting gear-side clutch surface is disposed.
 2. The electric retractable view device for a vehicle according to claim 1, wherein the one end face in the axis direction of the shaft outside-fitting gear has a structure in which the valley of the gear tooth of the shaft outside-fitting gear is occluded at all of radial positions from the tooth bottom to a tooth tip.
 3. The electric retractable view device for a vehicle according to claim 1, wherein the shaft outside-fitting gear-side clutch surface is disposed so as to reach a radial position of a tooth tip of the gear tooth in the radial direction of the shaft outside-fitting gear.
 4. The electric retractable view device for a vehicle according to, wherein a module of the shaft outside-fitting gear is not less than 0.6 and less than 1.0.
 5. The electric retractable view device for a vehicle according to claim 1, wherein: the clutch mechanism includes a clutch plate fitted on the outer circumference of the shaft; the clutch plate is formed of a material including a resin as a base material; the clutch plate includes a hollow to which the shaft is inserted, the shaft-side clutch surface is formed on an outer circumferential side of the clutch plate relative to the hollow; the shaft and the clutch plate each include a rotation preventing recess and a rotation preventing projection, in an outer circumferential surface of the shaft and an inner circumferential surface of the hollow of the clutch plate, respectively, the rotation preventing recesses and the rotation preventing projections being fitted to each other and thereby making the clutch plate movable in the axis direction of the shaft and unmovable in the direction around the axis; and the rotation preventing projection on the clutch plate side is formed so as to reach a position beyond a top of the clutch crest of the clutch plate in the axis direction of the clutch plate.
 6. The electric retractable view device for a vehicle according to claim 5, wherein: the clutch plate includes a barrel formed so as to reach the position beyond the top of the clutch crest in the axis direction of the clutch plate, in a center of a surface of the clutch plate as viewed in an axis direction of the clutch plate; an inner space of the barrel forms a part in an axis direction of the hollow of the clutch plate; a part of the rotation preventing projection on the clutch plate side, the part being formed at the position beyond the top of the clutch crest, is included in an inner circumferential surface of the barrel; and the shaft outside-fitting gear includes a barrel bearing in an inner circumferential surface of a hollow to which the shaft is inserted, the barrel bearing receiving the barrel in such a manner that the barrel is rotatable relative to the barrel bearing.
 7. The electric retractable view device for a vehicle according to claim 5, wherein the rotation preventing projection of the clutch plate is disposed at a position at which the rotation preventing projection overlaps the clutch crest of the clutch plate in a circumferential direction of the clutch plate.
 8. The electric retractable view device for a vehicle according to claim 1, wherein either or each of a component providing the shaft outside-fitting gear-side clutch surface and a component providing the shaft-side clutch surface includes a lightening hole in a top of the relevant clutch crest.
 9. The electric retractable view device for a vehicle according to claim 1, wherein either or each of a component providing the shaft outside-fitting gear-side clutch surface and a component providing the shaft-side clutch surface includes a lightening hole in a bottom of the relevant clutch valley.
 10. A shaft outside-fitting gear to be incorporated in an electric retractable view device for a vehicle, wherein: the shaft outside-fitting gear is formed of a material including a resin as a base material; the shaft outside-fitting gear includes a shaft outside-fitting gear-side clutch surface in one end face in an axis direction of the shaft outside-fitting gear; the shaft outside-fitting gear-side clutch surface is disposed on an inner circumferential side and an outer circumferential side of a radial position of a tooth bottom of a gear tooth of the shaft outside-fitting gear relative to the radial position of the tooth bottom, in a radial direction of the shaft outside-fitting gear; and the one end face in the axis direction of the shaft outside-fitting gear has a structure in which a valley of the gear tooth of the shaft outside-fitting gear is occluded at least at a radial region at which the shaft outside-fitting gear-side clutch surface is disposed.
 11. The electric retractable view device for a vehicle according to claim 2, wherein the shaft outside-fitting gear-side clutch surface is disposed so as to reach a radial position of a tooth tip of the gear tooth in the radial direction of the shaft outside-fitting gear.
 12. The electric retractable view device for a vehicle according to claim 6, wherein the rotation preventing projection of the clutch plate is disposed at a position at which the rotation preventing projection overlaps the clutch crest of the clutch plate in a circumferential direction of the clutch plate. 